Werner's syndrome (WS), a rare autosomal recessive disease due to mutations in a WRN helicase gene, is caused by genome instability. Patients affected with WS exhibit predisposition to cancer, and premature aging, accompanied by development of bilateral cataracts, diabetes mellitus, and osteoporosis. WRN helicase is a critical factor in DNA repair by homologous recombination, which repairs damage due to double strand breaks ((DSB) and stalled replication forks. The goal of this project is to understand how WRN functions in this pathway by examining the response of WRN to DNA damage; and its interactions with other factors. In normal cells and cells responding to DNA damage, WRN nuclear foci are clearly visible by immunofluorescent microscopy. It is not known whether this localization of WRN depends upon helicase activity, interactions with other factors, or both. The aims of this proposal are to determine whether WRN localization is dependent on helicase activity and/or interaction with RAD52, an important repair factor. I will use fluorescent microscopy to analyze localization of wild-type WRN, mutant WRN which lacks helicase activity, and mutant WRN which is unable to interact with RAD52; and compare localization in cells growing under normal conditions and cells treated with agents that cause DNA damage. These experiments will provide us with a clear picture of how WRN localizes in a living cell and if localization is dependent upon intrinsic enzymatic activity or interactions with other proteins. [unreadable] [unreadable]